1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for transmitting/receiving information through a fast feedback channel having limited capacity in a broadband wireless communication system.
2. Description of the Related Art
Physical channels for transmitting UpLink (UL) fast feedback information are present in Orthogonal Frequency Division Multiple Access (OFDMA)-based communication systems. Examples of the UL fast feedback information may include a variety of information, such as, a Signal-to-Noise Ratio (SNR) or a Carrier-to-Interference Ratio (CIR), a Modulation and Coding Scheme (MCS) preferred by a Mobile Station (MS), information for selecting a Flexible Frequency Reuse (FFR), a beam forming index, and the like.
The UL fast feedback information is small but is significantly important for operating a communication system. Thus, high reliability has to be ensured when the UL fast feedback information is transmitted. However, to avoid a waste of resources, a physical channel for transmitting high speed feedback information is not allocated generally with a large amount of frequency-time resources. Therefore, an effective modulation/demodulation scheme is required for reliable transmission using limited resources.
The OFDMA-based communication systems generally use non-coherent modulation/demodulation to transmit and receive the UL fast feedback information. Signal streams orthogonal to each other are used for the non-coherent modulation/demodulation. Thus, there is a restriction on the number of bits of information that can be transmitted using limited frequency-time resources. In addition, since the same signal is transmitted using different frequency resources to obtain a frequency diversity gain, a resource loss is greater than an information bit loss.
As described above, the fast feedback information is necessary for system operation and thus demands high reliability. However, resource utility efficiency may decrease by the orthogonal signal streams for ensuring high reliability and by the use of a diversity scheme.
Therefore, a need exists for an apparatus and method for effectively using resources in a broadband wireless communication system while maintaining high reliability.